Biotin/avidin formulation

Abstract

The present invention provides an improved biotin-avidin formulation in which a biotinylated antibody conjugate or an avidin-enzyme conjugate is present in a suitable diluent for immunohistochemical staining. The diluent additionally comprises casein in an amount sufficient to prevent charge interactions of the conjugate with a tissue section and gamma globulin in an amount sufficient to prevent Fc receptor binding and any hydrophobic interaction of the conjugate with a tissue section. In a preferred embodiment, the immunoglobulin is from the same species as the biotinylated antibody conjugate. The formulation effectively reduces overall unwanted binding, irrespective of the source of the binding.

What is claimed is: 
     
       1. A biotin-avidin formulation comprising a conjugate selected from the group consisting of a biotinylated antibody conjugate and an avidin-enzyme conjugate in a suitable diluent for immunohistochemical staining, said diluent additionally comprising: (a) casein in an amount sufficient to prevent charge interactions of the conjugate with a tissue section; and   (b) gamma globulin prepared from nonimmune serum in an amount sufficient to prevent Fc receptor binding and any hydrophobic interaction of the conjugate with a tissue section.   
     
     
       2. The formulation of claim 1 wherein casein is present at a concentration of from about 5 mg/ml to about 30 mg/ml. 
     
     
       3. The formulation of claim 2 wherein casein is present at a concentration of from about 10 mg/ml to about 15 mg/ml. 
     
     
       4. The formulation of claim 1 wherein the gamma globulin is present at a concentration of from about 1 mg/ml to about 50 mg/ml. 
     
     
       5. The formulation of claim 4 wherein the gamma globulin is present at a concentration of about 3 mg/ml. 
     
     
       6. The formulation of claim 1 wherein the conjugate is a biotinylated antibody. 
     
     
       7. The formulation of claim 6 wherein the antibody is selected from the group consisting of goat anti-rabbit IgG, goat anti-mouse IgG, and goat anti-mouse IgM. 
     
     
       8. The formulation of claim 6 wherein the gamma globulin is from the same species as the antibody. 
     
     
       9. The formulation of claim 1 wherein the conjugate is an avidin-enzyme conjugate. 
     
     
       10. The formulation of claim 9 wherein the enzyme is selected from the group consisting of horseradish peroxidase, alkaline phosphatase, and β-galactosidase. 
     
     
       11. A biotin-avidin detection system kit comprising: (a) in a first container, a biotinylated antibody conjugate; and   (b) in a second container, an avidin-enzyme conjugate, wherein the biotinylated antibody conjugate and avidin-enzyme conjugate are each present in a suitable diluent for immunohistochemical staining comprising casein in an amount sufficient to prevent charge interactions of the conjugate with a tissue section and gamma globulin prepared from nonimmune serum in an amount sufficient to prevent Fc receptor binding and any nonspecific hydrophobic interaction of the conjugate.   
     
     
       12. The biotin-avidin detection kit of claim 11 wherein the antibody is a goat antibody. 
     
     
       13. The biotin-avidin detection kit of claim 11 wherein the gamma globulin is from the same species as the antibody. 
     
     
       14. The biotin-avidin detection kit of claim 11 wherein the kit additionally comprises, in a third container, a substrate for the enzyme of the avidin-enzyme conjugate.